In the near future the Federal Communications Commission proposes to increase the number of available channels of citizens band usage to as high as 56. The expanded channels of communication make desirable a base loading coil assembly which is accurately tunable over a wide range of inductance values so as to permit the tuning of a single fixed length mobile transceiver antenna to a wide range of resonant frequencies. Such loading coil assemblies as are now known in the prior art often do not permit continuous accurate variation of inductance over such a wide inductance range, nor do they provide simple and accurate means for adjustment to specific inductance values on a repetitive basis. Also, moisture seepage into tunable antenna loading coils has been a problem in the prior art. My invention substantially overcomes these other difficulties known in the prior art.